New Study Shows Extreme Rainfall Not Increasing In England & Wales

By Paul Homewood  

 

The Met Office frequently claim that rainfall is becoming more intense in the UK. This claim stems in part from the study by Matthew Perry, “A spatial analysis of trends in the UK climate since 1914 using gridded dataset”.

This was the paper I mentioned a few days ago, with regard to sunshine hours trends. Although temperature and rainfall data is available to 1910 and before, the section on extreme rainfall only uses data since 1961. (There are other studies, but they also start from 1961, for instance here).

From that, they produce these two tables:

 

 

 

http://www.metoffice.gov.uk/media/pdf/q/h/UK_climate_trends.pdf

 

They conclude:

The increases in days of heavy rain and the greatest annual 5-days precipitation amounts suggest a tendency for an increasing likelihood for extreme heavy rainfall events.

 

As I have pointed out many times before, this choice of start date coincides with an unusually dry period. As flood expert, Prof Lane from Durham University states:

In terms of river flooding, the period since the early 1960s and until the late 1990s appears to be relatively flood free, especially when compared with some periods in the late 19th century and early 20th Century.

 

 

The England & Wales Precipitation Series provides daily data since 1931, so I have been able to replicate a couple of the tests that Matthew Perry made.

First, the average rain per rainday (defined as a day with >1mm), in other words, the average rainfall intensity calculated by Perry.

 

 

 

The lowest value was recorded in the 1960’s, and the 70’s were also notably dry. The 2000’s rank only 4th (not counting the 2005-14 period, included for comparison purposes only), and at 4.9mm are bang on average for the period.

If I had used 1961 as the start point, there would be the clear increasing trend, which Perry identified. However, looking at the record as a whole, there is nothing unusual about recent years, and certainly nothing which justifies the claim that extreme rainfall is either becoming more common or intense.

 

When we look at raindays over 10mm, we find a similar pattern, with less heavy rain days during the 1960’s and 70’s, and the two decades with most days being the 1950’s and 90’s.

 

 

 

However, when we look at really intense rainfall, days with more than 25mm, the pattern reverses, with the 1960’s and 70’s coming out top. Although the last ten years has had three such days, this is no more than during the 1970’s.

 

 

 

 

 

Finally, it should be remembered that the 1910’s and 20’s were also wet decades, and it would appear highly likely that both would be comparable with the 1950’s and 90’s as far as intense rainfall was concerned. Unfortunately, the Met Office do not provide data for this period, even though it must be available.   

 

https://notalotofpeopleknowthat.wordpress.com/2014/12/14/is-britain-getting-wetter/

 

As far as England & Wales are concerned, there is nothing in the data which provides evidence that “The increases in days of heavy rain and the greatest annual 5-days precipitation amounts suggest a tendency for an increasing likelihood for extreme heavy rainfall events”. Even winter months show no such trend, as I showed in an earlier post here.

For some reason, the Met Office don’t want the public to know any of this. Instead, they deliberately start their analysis in 1961, as Julia Slingo did in her report “Too hot, too cold, too
wet, too dry: Drivers and impacts of seasonal weather in the UK” , which was published in March 2014.  

It contained this highly misleading section (pp17-18):

 

 

Under their current management, the Met Office cannot be relied upon to provide the impartial advice we need.  

 

 

 

Source

The England & Wales Precipitation Series

http://www.metoffice.gov.uk/hadobs/hadukp/data/download.html